Efficient removal of heavy metal ions from aqueous media by unmodified and modified nanodiamonds

Adsorption of Cu(II) and Pb(II) in Aqueous Solution by Biochar Composites

In this study, straw biochar (TB) was prepared by pyrolysis at 500 °C, and biochar composite material (TBS) was prepared by a 1:4 mass ratio with sludge (TS). Scanning electron microscopy and Fourier transform infrared spectroscopy were utilized to characterize the material before and after adsorption. The results demonstrated that TBS possesses significant pore structure characteristics and abundant active functional groups such as hydroxyl, carboxyl, and carbonyl groups, providing a structural basis for its efficient adsorption of heavy metal ions in aqueous solutions. The adsorption performance of the remediation materials for Cu(II) and Pb(II) in aqueous solution was systematically investigated. Experimental data showed that TBS achieved maximum adsorption capacities of 60.86 and 46.98 mg/g for Cu(II) and Pb(II) at equilibrium, respectively, exhibiting superior adsorption efficiency. Through fitting analysis using adsorption kinetic models and isothermal adsorption models, it was found that the pseudo-second-order kinetic model and Freundlich isothermal model could more accurately describe the adsorption process of the two heavy metal ions, indicating that chemical adsorption was the dominant mechanism and characterized by multilayer adsorption. Thermodynamic parameter calculations revealed negative ΔG values and positive ΔH and ΔS values, suggesting that the adsorption process was a spontaneous, entropy-increasing, and endothermic reaction. These research results fully validate the excellent removal capabilities of TBS for Cu(II) and Pb(II). This study has shown that TBS can be considered a promising and cost-effective adsorbent, demonstrating its potential to adsorb heavy metal ions in water.

Impact of bacterial cell concentration on microbial-mediated cerium carbonate precipitation for efficient heavy metal removal: Insights from adsorption isotherm, kinetics, and thermodynamics

Heavy metals (HMs) pollution is a pervasive environmental issue needs significant attention through bioremediation. Present study investigated the potentiality of Microbial-mediated Cerium Carbonate Precipitation (MMCCP) in simultaneous removal of HMs (Cr, Pb, and Cu) using different cellular concentration of Sporosarcina pasteurii. Results from SEM analysis revealed formation of spherical and rod-like structures (∼112nm), and finally XRD and FTIR confirmed the formation of high-purity crystalline CeCO3OH with surface-bound hydroxyl groups and CO32- ions, indicating successful cerium incorporation and formation in CeCO3OH. Moreover, optimal removal efficiencies for Cr (99%), Pb (99%), and Cu (68%) were achieved within 80min at 6mg/L concentration and 0.05g adsorbent dose. Adsorption followed the Langmuir isotherm (R2 = 0.9) and pseudo-second-order kinetics, with thermodynamic parameters indicating spontaneity and exothermicity (ΔG < 0, ΔH < 0, ΔS > 0). These findings demonstrate MMCCP's potential as an effective and sustainable approach for HMs remediation.

Advances in graphene-based nanomaterials for heavy metal removal from water: Mini review

The environment and public health are seriously at risk from the increasing levels of heavy metal (HM) pollution in water bodies, hence efficient remediation techniques must be developed. Unique physicochemical properties of graphene (Gn) such as its enormous surface area, chemical stability, and extraordinary adsorption capabilities have made it a promising candidate for application in various adsorption processes. Recent studies indicate the heavy metal removal capabilities of Gn-based materials such as Gn oxide (GO) and reduced GO (rGO) reach 99% efficiency rates for lead (Pb2+), cadmium (Cd2+), and mercury (Hg2+) through strong electrostatic bonds and metal coordination along with π-π stacking interactions. In addition, the selective nature of Gn-based adsorbents grows better through functionalization because it incorporates thiol, amine, and sulfonic acid groups. The integration of Gn-based materials with metal-organic frameworks (MOFs) combined with magnetic nanoparticles along with bio-based polymers enhances adsorption efficiency and increases stability while offering recyclability features. The conclusion of this study discusses the current obstacles such as cost, scalability, environmental impact, and selectivity and potential future developments for the widespread use of Gn-based adsorbents in water treatment, highlighting the significance of continued research to improve these substances for useful environmental applications. PRACTITIONER POINTS: Graphene-based materials exhibit high capacity for adsorbing various heavy metals, enhancing water purification. Functionalization of graphene improves its ability to selectively target and remove specific heavy metals like mercury and lead. Graphene derivatives can achieve heavy metal removal within minutes, making them efficient for water treatment. Despite high synthesis costs, graphene's superior performance may lower long-term operational costs in wastewater treatment.

Carbonaceous adsorbents in wastewater treatment: From mechanism to emerging application

Adsorption is of great significance in the water pollution control. Carbonaceous adsorbents, such as carbon quantum dots, carbon nanotubes, graphene, and activated carbons, have long been deployed in sustainable wastewater treatment due to their excellent physical structure and strong interaction with various pollutants; these features allow them to spark greater interest in environmental remediation. Although numerous eye-catch researches on carbon materials in wastewater treatment, there is a lack of comprehensive comparison and summary of the vivid structure-activity-application relationships of different types of carbonaceous adsorbents at the molecular and atomic level. Herein, this review aims to scrutinize and contrast the adsorption mechanisms of carbonaceous adsorbents with different dimensions, analyzing the qualitative differences in adsorption capacity from microscopic perspectives, structural diversity caused by preparation methods, and environmental external factors affecting adsorption occurrence. Then, a quantitatively in-depth critical appraisal of traditional and emerging contaminants in wastewater treatment using carbonaceous adsorbents, and innovative strategies for enhancing their adsorption capacity are discussed. Finally, in the context of growing imposed circularity and zero waste wishes, this review offers some promising insights for carbonaceous adsorbents in achieving sustainable wastewater treatment.

Green synthesis of novel Zn0.5Ni0.5FeCrO4 spinel magnetic nanoparticles: Photodegradation of 4-nitrophenol and aniline under visible light irradiation

This study explores novel nanoparticles used in environmental remediation of 4-nitrophenol and aniline from wastewater bodies. The Zn0.5Ni0.5FeCrO4 magnetic nanoparticles (MNPs) were synthesized using tragacanth gel as a green, low-cost, and easy sol-gel method. The MNPs were characterized by XRD, XPS, FT-IR, VSM, TEM, EDX, FESEM, BET, DRS, and elemental mapping. The analysis demonstrated that nanoparticles have a spinel cubic structure, spatial distribution of the elements, ferromagnetic activity, narrow bandgap, and uniform morphology. Furthermore, effectiveness of the developed MNPs to degrade recalcitrant organic pollutants such as 4-nitrophenol (4-NP) and aniline under visible light exposure were studied. The results indicated 95% aniline and 80% of 4-NP were successfully degraded in 180 and 150 min, respectively. The total organic carbon (TOC) analysis revealed 65% and 54% removal of aniline and 4-NP. LC-MS was employed to elucidate the photodegradation mechanism and to identify the degradation products, including small fragmented molecules.

Dispersive micro-solid phase extraction (D-μSPE) of nickel on activated nanodiamonds@Bi2WO6 nanocomposite from water and food samples

This study presents an original nano-sorbent using activated nanodiamonds@Bi2WO6 to separate and enrich nickel ions from water and food samples. FTIR, XRD, FE-SEM, FE-SEM-EDX, EDS-TEAM, TGA, and BET were used to characterize the nanocomposite. It has a large surface area, active functional groups, and better reactivity. Ni(II) ions were determined as Ni(II)-PADAP chelates using UV-VIS spectroscopy. The parameters were studied and optimized, including pH (6), eluent type and volume (1 mL), ligand quantity (10 μg), sorbent dosage (20 mg), and contact time (1 min). The method has a low limit of detection (LOD) of 1.6 μg L-1, a limit of quantification (LOQ) of 5.3 μg L-1, a relative standard deviation of 4.5%, and a preconcentration factor of 10. The method was validated by applying to certified reference materials (BCR estuarine water 505 and 1573a NIST). The method was successfully applied to tap waters, industrial waste waters, and vegetables.

Carboxylated nanodiamonds@CuAl2O4@TiO2 nanocomposite for the dispersive micro-solid phase extraction of nickel at trace levels from food samples

Heavy metal pollution poses a significant health risk, necessitating regular environmental monitoring for public safety. Elevated nickel concentrations can disrupt ecosystems and impact human health. This study presents a nano-sorbent can be used for dispersive micro-solid phase extraction of nickel. The nano-sorbent was characterized using FT-IR, XRD, FESEM, BET, and BJH. It demonstrated remarkable efficiency due to its nanoscale properties, optimizing results in exceptional extraction performance with minimal interference from common ions. A flame atomic absorption spectrometer was utilized for all measurements. It has a low LOD (0.29 μg L-1) and RSDs% (7.3 % and 6 % intra-day and inter-day, respectively), minimal variation, and a precisely accurate correlation (0.997). It can be used on black tea, green tea, carrots, coffee beans, tuna fish, herring fish, tobacco, soil, natural water, and wastewater samples. The accuracy of the method was assessed by analyzing TMDA-64.3 fortified water and NIST 1573a tomato leaves certified reference materials.

Remarkable purification of organic dyes by NiOOH-modified industrial waste residues

Extracting functional materials from industrial waste residues to absorb organic dyes can maximize waste reuse and minimize water pollution. However, the extraordinarily low purification efficiency still limits the practical application of this strategy. Herein, the lamellar NiOOH is in-situ anchored on the industrial waste red mud surface (ARM/NiOOH) as an adsorbent to purify organic dyes in wastewater. ARM/NiOOH adsorbent with high specific surface area and porosity provides considerable active sites for the congo red (CR), thereby significantly enhancing the removal efficiency of CR. Besides, we fit a reasonable adsorption model for ARM/NiOOH adsorbent and investigate its adsorption kinetics. Resultantly, ARM/NiOOH adsorbent can remarkably adsorb 348.0 mg g-1 CR within 5 min, which is 7.91 times that of raw RM. Our work provides a strategy for reusing industrial waste and purifying sewage pollution, which advances wastewater treatment engineering.

Novel ZIF-8/CNC Nanohybrid with an Interconnected Structure: Toward a Sustainable Adsorbent for Efficient Removal of Cd(II) Ions

Water pollution, especially by heavy metals, continues to pose significant challenges, emphasizing the urgency to develop sustainable processes to remove pollutants while developing sustainable materials derived from renewable sources. In the present research, a nanoscale adsorbent was prepared to remove cadmium (Cd(II)) ions from wastewater by hybridizing zeolitic imidazolate framework-8 (ZIF-8) with a cellulose nanocrystal (CNC). The prepared nanohybrid exhibited an interconnected structure in which the ZIF-8 particles were connected to each other via CNC nanoneedles. The hybridization of ZIF-8 with CNC caused a significant enhancement in the adsorption performance of the fabricated nanohybrid compared to pure ZIF-8, increasing its adsorption capacity by nearly 36%. The adsorption of ZIF/CNC followed the Langmuir isotherm model and pseudo-second-order kinetics models, remarking homogeneous adsorption onto the surface of ZIF/CNC, where chemisorption controlled the rate of adsorption. The thermodynamic study uncovered that the adsorption is spontaneous, endothermic, and entropy-governed as the randomness was increased at the solid-liquid interface. Additionally, the influence of operating variables, such as temperature, adsorbent dosage, pH, and ionic strength, was studied to mimic the adsorption capabilities of the adsorbent in real conditions. Accordingly, the optimum conditions were found to be at 45 °C and pH = 7 with a dosage of 0.4 g/L for the adsorbent. Moreover, the adsorption in a multimetal solution showed that the ZIF/CNC nanohybrid can remove various heavy metals, including Cd(II), Fe(III), Cu(II), and Pb(II) ions simultaneously. Finally, the regeneration study confirmed the great potential of the ZIF/CNC nanohybrid, which retained 94% of its initial adsorption capacity after 5 consecutive adsorption/desorption cycles.

Towards a sustainable transformation of municipal wastewater treatment plants into biofactories using advanced NH3-N recovery technologies: A review

Ammonia (NH3), as a prevalent pollutant in municipal wastewater discharges, can impair aquatic life and have a negatively impact on the environment. Proper wastewater treatment and management practices are essential to protect ecosystems and keep human populations healthy. Therefore, using highly effective NH3-N recovery technologies at wastewater treatment plants (WWTPs) is widely acknowledged as a necessity. In order to improve the overall efficiency of NH3 removal/recovery processes, innovative technologies have been generally applied to reduce its concentration when discharged into natural water bodies. This study reviews the current status of the main issues affecting NH3 recovery from municipal/domestic wastewater discharges. The current study investigated the ability to recover valuable resources, e.g., nutrients, regenerated water, and energy in the form of biogas through advanced and innovative methods in tertiary treatment to achieve higher efficiency towards sustainable wastewater and resource recovery facilities (W&RRFs). In addition, the concept of paradigm shifts from WWTP to a large/full scale W&RRF has been studied with several examples of conversion to innovative bio-factories producing materials. On the other hand, the carbon footprint and the high-energy consumption of the WWTPs were also considered to assess the sustainability of these facilities.

Wastewater treatment using nanodiamond and related materials

Nanodiamonds (NDs) are zero-dimensional (0D) carbon-based nanoparticles with SP3/SP2-hybridized carbon atoms that have shown great potential in wastewater treatment areas due to their high surface area, chemical stability, and unique adsorption properties. They can efficiently remove a wide range of pollutants from water, including heavy metals, organic compounds, and dyes via various mechanisms such as electrostatic interactions, π-π stacking, and ion exchange. NDs can be functionalized following different surface chemistries, enabling tailored surface properties and enhanced pollutant adsorption capabilities. This review covers recent research on the application of nanodiamonds in wastewater treatment domain with a major emphasis on adsorption, photocatalytic degradation, and membrane separation, highlighting their promising performances, challenges, and future directions.

In situ synthesis of multivariant zeolitic tetrazolate imidazole frameworks (ZTIFs) with uncoordinated N-heteroatom sites for efficient adsorption of antiviral drugs

The current outbreak of the coronavirus (COVID-19) pandemic has significantly increased the global usage of antiviral drugs (AVDs), leading to higher concentrations of antibiotics in water pollution. To address this current issue, a new kind of adsorbent named isostructural zeolitic tetrazolate imidazolate frameworks (ZTIFs) were synthesized by combining imidazole and tetrazolates into one self-assembly approach by adjusting pores and stability of frameworks. The incorporation of imidazole ligand progressively increased the stability of frameworks. Furthermore, increasing the content of tetrazolate ligand greatly improved the adsorption performance due to N-rich sites by increasing the pore size. The obtained adsorbent composite exhibits macroporous structure up to 53.05 nm with excellent structural stability. Owing to their macropores and highly exposed active sites, the synthesized ZTIFs exhibit the maximum adsorption capacity for oseltamivir (OT) and ritonavir (RT) of 585.2 mg/g and 435.8 mg/g, respectively. Moreover, the adsorption uptake and saturation process were rapid compared to simple MOF. Within 20 min, both pollutants achieved equilibrium. The adsorption isotherms were best interpreted by Pseudo second order kinetics. The adsorption of AVDs on ZTIFs was spontaneous, exothermic, and thermodynamically feasible. The DFT calculations and characterization results after adsorption demonstrate that π-π interaction, pore filling, surface complexation, and electrostatic interaction were the primary features of the adsorption mechanism. The prepared ZTIFs composite exhibits high chemical, mechanical and thermal stability and can be recycled multiple times without destroying its morphology and structure. The adsorbent regeneration for several cycles impacted the operational cost and the eco-friendly characteristic of the process.

Magnetic Nitrogen-Rich UiO-66 Metal-Organic Framework: An Efficient Adsorbent for Water Treatment

The postsynthetic modification of metal-organic frameworks (MOFs) has opened up a promising area to widen their water treatment application. However, their polycrystalline powdery state still restricts their widespread industrial-scale applications. Herein, the magnetization of UiO-66-NH₂ is reported as a promising approach to facilitate the separation of the used MOFs after water treatment. A two-step postmodification procedure employing 2,4,6-trichloro-1,3,5-triazine (TCT) and 5-phenyl-1H-tetrazole (PTZ) agents was introduced to level up the adsorption performance of the magnetic nanocomposite. Despite a decrement in porosity and specific surface area of the designed MOFs (m-UiO-66-TCT) compared to neat UiO-66-NH₂, it outweighs in adsorption capacity. It was observed that m-UiO-66-TCT has an adsorption capacity of ≈298 mg/g for methyl orange (MO) with facile MOF separation using an external magnet. Pseudo-second-order kinetic model and Freundlich isotherm models suitably interpret the experimental data. Thermodynamic studies showed that MO removal using m-UiO-66-TCT is spontaneous and thermodynamically favorable at higher temperatures. The m-UiO-66-TCT composite exhibited easy separation, high adsorption capacity, and good recyclability, rendering it an attractive candidate for the adsorptive removal of MO dye from aqueous environments.

Heavy metal pollution in the aquatic environment: efficient and low-cost removal approaches to eliminate their toxicity: a review

Heavy metal contamination of water sources has emerged as a major global environmental concern, threatening both aquatic ecosystems and human health. Heavy metal pollution in the aquatic environment is on the rise due to industrialization, climate change, and urbanization. Sources of pollution include mining waste, landfill leachates, municipal and industrial wastewater, urban runoff, and natural phenomena such as volcanic eruptions, weathering, and rock abrasion. Heavy metal ions are toxic, potentially carcinogenic, and can bioaccumulate in biological systems. Heavy metals can cause harm to various organs, including the neurological system, liver, lungs, kidneys, stomach, skin, and reproductive systems, even at low exposure levels. Efforts to find efficient methods to remove heavy metals from wastewater have increased in recent years. Although some approaches can effectively remove heavy metal contaminants, their high preparation and usage costs may limit their practical applications. Many review articles have been published on the toxicity and treatment methods for removing heavy metals from wastewater. This review focuses on the main sources of heavy metal pollution, their biological and chemical transformation, toxicological impacts on the environment, and harmful effects on the ecosystem. It also examines recent advances in cost-effective and efficient techniques for removing heavy metals from wastewater, such as physicochemical adsorption using biochar and natural zeolite ion exchangers, as well as decomposition of heavy metal complexes through advanced oxidation processes (AOPs). Finally, the advantages, practical applications, and future potential of these techniques are discussed, along with any challenges and limitations that must be considered.

Adsorption of sulfanilamides using biochar derived from Suaeda salsa: adsorption kinetics, isotherm, thermodynamics, and mechanism

Suaeda biochar (SBC) was prepared by muffle furnace with Suaeda salsa at 600, 700, 800, and 900 ℃. The physical and chemical properties of biochar at different pyrolysis temperatures and the adsorption mechanism of sulfanilamide (SM) were studied by SEM-EDS, BET, FTIR, XRD, and XPS analysis. The adsorption kinetics and adsorption isotherms were fitted. The results showed that the kinetics was in line with the quasi-second-order adsorption model and belonged to chemisorption. The adsorption isotherm conformed to Langmuir adsorption isotherm model and belonged to monolayer adsorption. The adsorption of SM on SBC was spontaneous and exothermic. The adsorption mechanism may be pore filling, hydrogen bonding, and π-π electron donor acceptor (EDA) interaction.

Synthesis of Fe-THC MOFs and functionalizing MOFs by MXenes for the selective removal of lead(ii) ions from wastewater

The elimination of heavy metals, especially lead, from wastewater is vital for the environment and human health and using a proper adsorbent to achieve this goal is highly desirable. Initially, Fe-THC MOF was prepared using a simple method and functionalized using MXene for efficient, rapid, and selective elimination of lead. Different characterization tools demonstrated that Fe-THC MOF and its composite Fe-THC/MXene were successfully prepared. The adsorption outcomes showed that the maximum sorption capability was 674 mg g^-1 at 305 K and pH 4.5. The sorption kinetics obeys the pseudo-second-order kinetic model, and the sorption isotherms fit the Langmuir isotherm model. This finding suggests monolayer sorption on Fe-THC/MXene, and the rate-controlling step is chemisorption. Thermodynamic findings exhibit that sorption was a spontaneous and exothermic process. The sorption process can selectively adsorb Pb ions from aqueous media. After five adsorption-desorption tests, the adsorption efficiency of Fe-THC/MXene was still high. The sorption mechanism of lead on Fe-THC was mainly due to the interaction of lead ions with -F and -O ions and porosity of the Fe-THC/MXene composite. The -O and -F ions were derived from MXene, while the porosity was derived from the MOFs of composites. These findings confirmed that Fe-THC/MXene enables rapid, efficient, and selective elimination of lead from wastewater, which is of practical importance.

Metal-organic frameworks: A promising option for the diagnosis and treatment of Alzheimer's disease

Beta-amyloid (Aβ) peptide is one of the main characteristic biomarkers of Alzheimer's disease (AD). Previous clinical investigations have proposed that unusual concentrations of this biomarker in cerebrospinal fluid, blood, and brain tissue are closely associated with the AD progression. Therefore, the critical point of early diagnosis, prevention, and treatment of AD is to monitor the levels of Aβ. In view of the potential of metal-organic frameworks (MOFs) for diagnosing and treating the AD, much attention has been focused in recent years. This review discusses the latest advances in the applications of MOFs for the early diagnosis of AD via fluorescence and electrochemiluminescence (ECL) detection of AD biomarkers, fluorescence detection of the main metal ions in the brain (Zn2+, Cu2+, Mn2+, Fe3+, and Al3+) in addition to magnetic resonance imaging (MRI) of the Aβ plaques. The current challenges and future strategies for translating the in vitro applications of MOFs into in vivo diagnosis of the AD are discussed.

Adsorption Behavior of a Gd-Based Metal-Organic Framework toward the Quercetin Drug: Effect of the Activation Condition

A carboxylate gadolinium-based metal-organic framework (Gd-MOF) is an exceptional candidate for magnetic resonance imaging agents, but its low drug adsorption capacity hinders this MOF from being used as a theragnostic agent. In this work, the Gd-MOF was synthesized by a simple solvothermal method. Then, different activation situations, including various solvents over different time periods, were applied to enhance the specific surface area of the synthesized MOF. Different characterization analyses such as X-ray diffraction and Brunauer-Emmett-Teller along with experimental quercetin adsorption tests were done to study the crystalline and physical properties of various activated MOFs. In the following, the MOF activated by ethanol for 3 days (3d-E) was chosen as the best activated MOF due to its crystallinity, highest specific surface area, and drug adsorption capacity. More explorations were done for the selected MOF, including the drug adsorption isotherm, thermodynamics, and pH effect of adsorption. The results show that the activation process substantially affects the crystallinity, morphology, specific surface area, and drug adsorption capacity of Gd-MOFs. An optimized activation condition is proposed in this work, which shows an impressive enhancement of the specific surface area of Gd-MOFs just by simple solvent exchange method employment.

Applications of Nano Hydroxyapatite as Adsorbents: A Review

Nano hydroxyapatite (Ca10(PO4)6(OH)2, HAp) has aroused widespread attention as a green and environmentally friendly adsorbent due to its outstanding ability in removing heavy metal ions, radio nuclides, organic pollutants and fluoride ions for wastewater treatment. The hexagonal crystal structure of HAp supports the adsorption mechanisms including ionic exchange reaction, surface complexation, the co-precipitation of new partially soluble phases and physical adsorption such as electrostatic interaction and hydrogen bonding. However, nano HAp has some drawbacks such as agglomeration and a significant pressure drop during filtration when used in powder form. Therefore, instead of using nano HAp alone, researchers have worked on modificationsand composites of nano HAp to overcome these issues and enhance the adsorption capacity. The modification of cationic doping and organic molecule grafting for nano HAp can promote the immobilization of ions and then increase adsorption capacity. Developing nano HAp composite with biopolymers such as gelatin, chitosan and chitin has proven to obtain a synergetic effect for improving the adsorption capacity of composites, in which nano HAp fixed and dispersed in polymers can playmuch more of a role for adsorption. This review summarizes the adsorption properties and adsorbent applications of nano HAp as well as the methods to enhance the adsorption capacity of nano HAp.